In recent years, NAND type flash memories having a two-dimensional structure are confronting the limit of scaling. Under the circumstances, there have increased the demands for a vertical type nonvolatile memory technique that can realize a larger memory capacity by use of integration based on stacking of layers without depending on scaling, and so a nonvolatile memory device having a vertical NAND structure, in which NAND strings are vertically arranged, has been proposed. For the nonvolatile memory device having a vertical NAND structure, a process technique is used such that it performs formation of word lines (control gate electrodes) stacked as layers, and formation of a stepwise lead-out part for leading out electrodes from the word lines.
In general, a metal material having a resistivity lower than poly-silicon is used for word lines. However, it is difficult to perform high aspect etching all together to a layered body composed of oxide films and metal films. In consideration of this problem, there is used a technique called replacement, which includes etching a layered body composed of oxide films and sacrificial films, then removing the sacrificial films, and then embedding a metal material into the gap spaces formed by removing the sacrificial films. In this case, columnar patterns are formed in the stepwise lead-out part before the replacement so that they can support the oxide films to prevent them from collapsing. The columnar patterns are vertically formed on the semiconductor substrate.
However, a film stress acts on the columnar patterns during the replacement, and causes the columnar patterns to be inclined, as the case may be. As a result, there may be a case that the columnar patterns thus inclined come into contact with contact patterns present adjacent to the word lines and formed to connect with the word lines. In the case that the columnar patterns include a conductive film, if the columnar patterns and the contact patterns come into contact with each other, a leakage current flowing through the columnar patterns into the silicon substrate is generated.